<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parent{
            width: 500px;
            height: 1000px;
            padding: 100px;
            box-sizing: border-box;
            border: 1px solid red;
            position: relative;
        }
        .one{
            width: 50%;
            height: 50%;
            border: 1px solid green;
            padding: 5%;
            margin: 5%;
            position: absolute;
        }
    </style>
</head>

<body>
    <div class="parent">
        <div class="one"></div>
    </div>
</body>

</html>